Enhanced Electrocatalytic N₂ Reduction to NH₃ Through Piezo-Assisted Polarization

Despite recent advances in sustainable chemical synthesis, finding technically feasible solutions for the fixation of nitrogen (N₂) remains challenging. The N₂ fixation yields ammonia (NH₃), a molecule with a high energy content (18.8 MJ kg^-1) and low storage costs. For more than a century the Haber-Bosch method has been used for the NH₃synthesis, a procedure that demands high temperatures (400 - 600 °C) and pressures (20 – 40 MPa).<font size="1"> </font>To achieve a more time- and cost-effective process, electrochemical NH₃ production arises as a feasible path to synthesize a green fertilizer with zero carbon footprint. In the recent years, piezoelectric materials come to the fore, which can be activated through mechanical vibrations, thereby decreasing the overpotential which is required to perform the nitrogen reduction reaction. Herein we present Na_0.5K_0.5NbO₃ (KNN) as a piezoelectric material which was synthesized via the sol-gel route using the corresponding alkoxides as precursors and deposited on stainless steel by spray coating. The catalytic activity can further be influenced by introducing silver as co-catalyst on the synthesized KNN layer. This work will address the use of the as-synthesized piezoelectric working electrode (KNN + Ag) for the piezo-enhanced nitrogen fixation. It was observed that the created transient dipoles in surface-absorbed non-polar N₂ molecule increases the N₂ coverage on the electrocatalyst surface. Furthermore, the ammonia production could be enhanced by 46 % with vibration assisted catalysis compared to without piezo-actuation.